Circuit interrupter



May 22, 1934. J. SLEPIAN CIRCUIT INTERRUPTER Filed Oct. 21. 1931 l N V EN TO R .jse oh 5/ 0/1470.

WITNESSES:

'ATT6RN Y 42 Ma K Patented May 22, 1934 CIRCUIT INTERBUPTER JosephSlepian, Pittsburgh, Pa., assignor to Westinghouse Electric &Manufacturing Company, a corporation of Pennsylvania Application October21, 1931, Serlal No. 570,132

' 18 Claims. (01.200-120) My invention relates to circuit interruptersand more particularly to a fuse for interrupting high voltage circuits.In the circuit interrupter of my invention, the arc is extinguished bythe 9 generation of gas, due to the decomposition of material along thearc stream to cause turbulence, resulting in volumes of fresh un-ionizedgas being in-mixed with the hot are gases to deionize them.

An object of my invention is to provide members of a solid materialalong the arc path which, when acted upon by the arc, give off a. largevolume of a condensable gas. These members of gas generating materialare positioned at spaced intervals, and means for condensing the gas areprovided in these spaces. This makes possible the construction of a highvoltage fuse wherein great length is not necessary in order to givesufiicient insulation between the terminal members, since the provisionof condensers at spaced intervals between the gas generating materialrelieves the pressure within the circuit interrupter and makes itunnecessary to leave an opening therethrough of such size as to allowthe escape of gas as in an expulsion fuse. This arrangement of alternatecondensers and gas generating means also makes it possible to use asmaller opening through the walls of gas generating material, since itis not necessary to provide openings of such size as would be necessaryto permit a flow of all of the gas through the openings out the end ofthe tube. This allows the gas generating material to be positionedcloser to the are where it will be more readily decomposed and where itwill be more efiective in extinguishing the arc.

Another object of my invention is to provide insulating spacers betweenthe sections of the gas generating material so as to allow the use of a.material which is desirable from the standpoint of amount of gasgenerated, but which may not retain its insulating properties at hightemperatures. This construction maintains the total dielectric strengthalong the arc path at a high value even though the molten surface of thegas generating material may be somewhat conducting.

A further object of my invention is to provide a fuse which is entirelyenclosed and self-contained and out of which there is no blast of hotionized gases which may come in contact with adjacent apparatus, thusmaking the interruption of the circuit quiet and safe.

These and other objects and advantages 01' my invention will be morefully apparent from the following description and the drawing, in whichFigure 1 is a view, partially in side elevation and partially inlongitudinal cross section, of a fuse embodying my invention, and

Fig. 2 is a sectional view taken transversely through the fuse on theline II-II of Figure 1.

In the embodiment of my invention illustrated on the drawing, a tubularcasing 5 of fiber or other suitable insulating material having goodmechanical strength is provided. The ends of the tubular casing 5 areclosed by metal cap members '7 secured to the tube 5 by any suitablemeans such as a screw thread. Within the tubular casing 5 are positioneda plurality of members 9 of a material which, when acted upon by thearc, evolve a gas which may be readily condensed. Each of the members 9of gas generating material is in the form of a solid disk which fitswithin the fiber tube 5 and is provided with an opening 11 through thecenter thereof. The disks 9 of gas generating material are provided atspaced intervals along the whole length of the tubular casing and arespaced apart by condensers in the form of a plurality of annular metalrings 13 which are spaced apart by annular rings of insulating material15. A fusible element 17 extends through the aligned openings in thedisks of gas generating material 9 and the annular metal rings 15 and iselectrically connected to each of the metal cap members 7 as by solder19.

The disks 9 of gas generating material may be of any desirable materialwhich has the property of giving oil a condensable gas when acted uponby the arc. It has been found that materials such as boric acid, gypsumand ammonium alum may be used for this purpose.

One of the most desirable materials is boric acid, since it may bereadily compressed by the application of pressure into solid cakes whichhave such mechanical strength that they may be used without difficulty.When boric acid (H'aBOa) is acted upon by the are, it is decomposed,giving off water vapor (H2O) and leaving boric oxide (B203) The 1 0water vapor given off is effective in causing turbulence to in-mixvolumes of fresh un-ionized gas with the arc to deionize it, and, sincethe water vapor is non-inflammable, there is no danger of an explosionwhich might rupture the casing of the fuse. The water vapor afterpassing through the arc comes in contact with the metal plates 13positioned between the disks 9, and since the metal plates 13 are at arelatively low temperature, the water vapor is condensed, thus relievingthe gas pressure within the container. The use of boric acid is alsodesirable, since it is an extremely good insulator and retains itsinsulating properties even when it has been heated to a high temperatureand is in. a molten state. Another advantage of boric acid is that it isnon-hygroscopic, thus repelling water so that it does not lose itsinsulating properties if placed in a humid atmosphere.

For some applications it has been found that the material for supplyingthe deionizing gas may be gypsum (CaSO42HzO), which is a calciumsulphate having water combined therewith. This material is decomposed bythe arc giving off water vapor (H2O), sulphur dioxide (S02) and oxygen(02) leaving solid calcium oxide (CaO). While gypsum does not giveresults anywhere near as good as boric acid, it may be used in circuitinterrupters where very high interrupting capacities are not necessary.

A material which is particularly adapted for use in the structure ofthis application is ammonium alum (Al2(NH4)2(SO4) 424H2O). This isdecomposed by the are giving off water vapor (H2O), sulphur dioxide(S02), ammonia (NH3) and leaving the solid aluminum oxide (A1203).Ammonium alum is superior to boric acid from the standpoint of volume ofgas evolved, but it does not maintain its insulating properties at thehigh temperatures to which it is subjected by the arc. While ammoniumalum is a good insulator when cold, it melts at 89 C. and becomes a goodconductor. It loses water rapidly at 150 C. so that this may be takenfor the temperature of rapid decomposition. This means that the surfaceleft immediately after the arc extinguishing will be an electricallyconducting film of the molten saltv which will break down under voltageand restart the arc unless other insulation is provided along the arcpath. The use of ammonium alum is made possible with the structure ofthis invention, since the members 9 when of ammonium alum are spacedfrom each other by the metal rings 13 and the insulating rings 15 sothat there is no continuous surface of ammonium alum extending along thearc path from one terminal of the fuse to the other.

From the above description of the specific modification of my inventionillustrated on the drawing, it is apparent that I have provided a fusewhich is extremely efiective for interrupting high voltage circuits andwhich overcomes the objections which have been present in expulsionfusesnow used for this service. While my invention has been illustrated asbeing applied to a fuse, it should be understood that the structure maybe readily modified so as to be used in a circuit breaker withoutdeparting from the spirit of my invention. Other changes andmodifications may be made without departing from my invention as definedin the following claims.

I claim as my invention:

1. Inan arc extinguishing device, means positioned along the arc path atspaced intervals for supplying a gas, a substantial part of which isreadily condensable, for extinguishing the arc, and means between saidspaced gas supplying means for condensing said gas.

2. In an arc extinguishing device, means along the arc path including aplurality of members of a material which gives off a gas, a substantialpart of which is non-inflammable and readily condensable, when actedupon by the arc, said members having spaces therebetween, and meansoccupying a part of said spaces for condensing the gas given off by saidmaterial.

3. In an arc extinguishing device, means along the arc path including aplurality of members of a material which is a solid at ordinary temperatures and which gives off a gas, a substantial part ofwhich is readilycondensable, when acted upon by the are, said members having spacestherebetween,v and a plurality of metallic members in said spaces forcondensing the gas given oil by said material.

4. In an arc extinguishing device, means of solid material positionedalong the arc path, at spaced intervals, for evolving water vapor, underinfluence of the arc, and condensing means positioned between saidspaced, vapor supplying means.

5. In an arc extinguishing device, means defining an opening in whichthe arc plays, said. means including members which generate a gas, asubstantial part of which is readily condensable, when exposed to thearc, and metallic members positioned between some of said gas generatingmembers for condensing said gas.

6. In an arc extinguishing device, a chamber surrounding the arc pathand closed on its sides,

openings therethrough forming a chamber for the arc, and a plurality ofsheets of metal between each' of said disks for condensing said gas.

8. In an arc extinguishing device, members of boric acid positionedalong the arc path for giving ofi water vapor under action of the arc,and condensing means positioned between said members of boric acid forcondensing said water vapor.

9. In a circuit interrupter, a closed chamber having a pair of externalelectrical terminal members, and means within said chamber andelectrically connected to said terminal members .for causing an arc, aportion of the walls of said chamber comprising solid members positionedat spaced intervals along the path of said are 10. In a circuitinterrupter, a tubular insulating casing, electrical terminal membersclosing the ends of said casing, aplurality of disks of a solid materialpositioned within said casing at spaced intervals and of a materialwhich gives off a non-inflammable, condensable gas when acted upon bythe arc, said disks having openings therethrough, a plurality of annularmetal rings positioned between said disks, and a fusible elementelectrically connected to said terminal members and extending throughthe openings in said disks and said annular rings.

11. In an arc extinguishing device, solid members positioned along thearc path which when acted upon by the arc evolve a gas for extinguishingthe arc, and insulating means having a greater dielectric strength whensubjected to the action of the arc than said gas evolving meansinterposed among said gas evolving means for improving the overallinsulating qualities thereof.

12. In an arc extinguishing device, a plurality of solid members alongthe arc path, said members being of a material which gives ot! a gas forextinguishing the arc, and means of a material having a greaterdielectric strength when subjected to the action of the arc than saidgas evolving material for insulating the surfaces of said solid membersadjacent the are from each other and thereby maintaining high resistanceacross the surfaces of said members along the arc path.

13. In an arc extinguishing device, means along the arc path which whenacted upon by the arc evolves a gas for extinguishing the arc, andinsulating inserts, of a material having a greater dielectric strengthwhen subjected to the action of the arc than said gas evolving material,positioned in the surface of said gas evolving means along the arc pathfor maintaining the dielectric strength along said surface when it is ata high temperature due to the arc.

14. In an arc extinguishing device, a chamber in which the arc plays,said chamber having walls along the arc path including alternate membersof insulating material and members which give off an arc extinguishinggas when acted upon by the arc, the dielectric strength of said membersof insulating material being greater than the dielectric strength ofsaid gas producing members when both are subjected to the action of thearc.

15. In an arc extinguishing device, means along the are path of ammoniumalum for giving oil a gas for extinguishing the arc, and insulating gapsin the surface of the ammonium alum for maintaining high dielectricstrength along said surface when acted upon by the arc.

16. In an arc extinguishing device, a material along the arc path whichevolves a gas, a substantial part of which is readily condensable, whensubjected to the influence of the are, metallic means for condensingsaid gas positioned at spaced intervals along the arc path, andinsulating gaps in the gas evolving material having a greater dielectricstrength when subjected to the action of the arc than said gas evolvingmaterial for maintaining the dielectric strength along the arc pathduring the circuit interrupting operation.

17. In an arc extinguishing device, a plurality of disks of a solidmaterial which gives oiT a gas, a substantial part of which is readilycondensable. when acted upon by an arc, said disks having openingstherethrough forming a chamber for the arc, a plurality of sheets ofmetal between said discs for condensing said gas, and insulating meansbetween said discs for maintaining the dielectric strength along the arcpath at a high value.

18. In a circuit interrupter, a tubular insulating casing, electricalterminal members closing the ends of said casing, a plurality of disksof a solid material positioned within said casing at spaced intervalsand of a material which gives ofi a gas, substantially all of which isnon-inflammable and readily condensable, when acted upon by the are,said disks having openings therethrough, a plurality of annular metalrings positioned between said disks, and a plurality of annular rings ofinsulating material positioned between said annular metal rings.

JOSEPH SLEPIAN.

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